In reactive processing, the processing equipment for melt-kneading of polymer is also used as reactor. In particular, so-called “reactive extrusion processing,” which uses an extruder, has high industrial value-added and therefore, is utilized very actively over the world.
For carrying out reactive processing in an extruder, the extruder has to meet many requirements with respect to temperature control, reaction time (retention time) to be ensured, uniform dispersion of catalysts, and effective removal of by-products. Ensuring a sufficient reaction time (retention time), in particular, is a very important factor in controlling the reaction in the extruder. Thus, extruders with a large ratio (L/D) between the screw length (L) and the screw diameter (D) have been used as a means of ensuring a reaction time (retention time) in the extruder, and for instance, the use of an extruder with a L/D ratio of 50 or more for reactive processing has been disclosed (see Patent document 1).
In addition, a production method using a stretched flow instead of a shear flow, which is commonly used for melt-kneading, has been proposed (see Patent document 2).
Also disclosed is a production process for a resin composition and impact absorbing material wherein their elastic modulus decreases and flexibility increases as the ratio (L/D) between the screw length (L) and the screw diameter (D) of the extruder is increased to raise the reactivity and tension speed (see Patent document 3).    [Patent document 1] Japanese Unexamined Patent Publication (Kokai) No. 2006-347151    [Patent document 2] Japanese Unexamined Patent Publication (Kokai) No. 2006-66025    [Patent document 3] Japanese Unexamined Patent Publication (Kokai) No. 2006-89701